1. Field of the Invention
The present invention relates to a method for geometric deformation of a seismic image in order to eliminate the effect of the deformations undergone by the subsoil after its deposition. The method applies to the interpretation of seismic sections or cubes. It relates to the geometric deformation of a seismic image (section or cube) in order to make the seismic interpreter's work simpler and to allow easier interpretation control. The data handled are the seismic depth images, cube or section, and characteristic surfaces (or horizons) obtained by picking on the seismic images themselves. Without geometric transformation, these seismic images and these surfaces correspond to a current state of the subsoil and not to its state at the geologic time of deposition of these surfaces. In fact, the subsoil undergoes considerable deformations during the geologic times that follow its deposition.
2. Description of the Prior Art
The geometric transformation of an image by means of a computer procedure is an operation that nowadays does not pose technical problems. However, the characterization of the parameters of geometric transformation remains in some cases a difficult operation.
In the field of interpretation of seismic images notably, two types of transformation are available to users:
1. “Flattening” of the horizons: Flattening carries out a translation of the seismic traces making up the seismic image, parallel to their axis, that is vertically, in order to reposition the traces so that their intersection with a geologic surface located along the traces is placed horizontal. This procedure is explained in FIG. 1b. It restores the image of the subsoil at the time of its deposition, provided that the topography at the time is absolutely horizontal.
2. Restoration. Restoration is performed by:
manually splitting the image into pieces;
performing geometric transformations of each piece individually; and then
reconstructing the total image by displacing the pieces, (as if putting the pieces of a jigsaw puzzle together again). For example, the Baliss and EasyDepth softwares from the Beicip-Franlab company can perform reconstruction.
The parameters of these various operations are entirely determined by the user.
In addition to the seismic image deformation techniques, the emergence of stratigraphic modelling can also be noted, with a goal to better apprehend the geometric (but also sedimentologic) structure of the subsoil, as well as its evolution during geologic times. These techniques may remain quite delicate to implement, but a recent evolution, described in document French Patent Application 03/11,194, which corresponds to U.S. Pat. No. 7,117,091, allows direct calculation of an estimation of the regional topography at the time of the deposition of a given sediment layer, from the thickness of this layer, that can be read on the seismic image.